Ion guide, a method of manipulating ions using an ion guide, a method of mass spectrometry, a mass spectrometer and computer software

Abstract

Ion guides comprise an inlet region for receiving a packet of ions; a first outlet region for ejecting ions; a second outlet region for ejecting ions; and a beam splitting electrode arranged to direct a first portion of the packet of ions towards the first outlet region and a second portion of the packet of ions towards the second outlet region.

We claim: 
     
         1 . An ion guide comprising:
 an inlet region for receiving a packet of ions;   a first outlet region for ejecting ions;   a second outlet region for ejecting ions;   a plurality of electrodes for applying a DC gradient, wherein the DC gradient urges ions away from the inlet region and towards the first and/or second outlet regions, wherein the plurality of electrodes are disposed on a first surface of an ion beam splitter, wherein the plurality of electrodes are radio frequency, RF, electrodes arranged to generate a pseudopotential surface; and   a beam splitting electrode arranged to direct a first portion of the packet of ions towards the first outlet region and a second portion of the packet of ions towards the second outlet region.   
     
     
         2 . The ion guide of  claim 1 , wherein a DC repeller is disposed on a second surface of the ion beam splitter opposite the first surface, wherein the inlet region, the first outlet region and the second outlet region are between the first surface and the second surface. 
     
     
         3 . The ion guide of  claim 1 , further comprising one or more electrodes disposed on a second surface of the ion beam splitter opposite the first surface, wherein the inlet region, the first outlet region and the second outlet region are between the first surface and the second surface. 
     
     
         4 . The ion guide of  claim 1 , wherein the beam splitting electrode comprises an apex between the first and second outlet regions. 
     
     
         5 . The ion guide of  claim 4 , wherein the apex is off-centre with respect to a central longitudinal axis of the ion guide. 
     
     
         6 . A method of manipulating ions using an ion guide, the ion guide comprising:
 an inlet region;   a first outlet region;   a second outlet region;   a plurality of electrodes disposed on a first surface of an ion beam splitter; and   a beam splitting electrode,   
       the method comprising:
 injecting a packet of ions via the inlet region; 
 applying a radio frequency signal to the plurality of electrodes to generate a pseudopotential surface; and 
 applying a longitudinal DC gradient to the plurality of electrodes to urge ions away from the inlet region and towards the first and/or second outlet regions; and using the beam splitting electrode to direct a first portion of the packet of ions towards the first outlet region and a second portion of the packet of ions towards the second outlet region. 
 
     
     
         7 . The method of  claim 6 , wherein the method further comprises:
 applying a lateral DC gradient to the plurality of electrodes to urge ions away from the first outlet region and towards the second outlet region, to adjust a relative proportion of the packet of ions that makes up the first and second portions; and/or   applying a lateral DC gradient to the plurality of electrodes to urge ions away from the first outlet region and towards the second outlet region, so that substantially all of the ions in the packet of ions are directed via the second outlet region.   
     
     
         8 . A method of mass spectrometry comprising the steps of:
 for each of a plurality of sub-ranges selected from an overall m/z range:
 configuring an ion guide to direct ions towards a first ion destination and a second ion destination, wherein the first ion destination is a first ion store; and 
 accumulating in the first ion store a sample of precursor ions to be analysed, the precursor ions having m/z values within the sub-range; 
   wherein either:
 a) the second ion destination is a first mass analyser, and wherein the method further comprises injecting a sample of fragmented precursor ions into the first mass analyser, or 
 b) the second ion destination is a second ion store, and wherein the method further comprises accumulating in the second ion store a sample of fragmented precursor ions for analysis in a first mass analyser, 
   wherein the sample of fragmented precursor ions are formed from fragmentation of precursor ions having m/z values within the sub-range.   
     
     
         9 . The method of  claim 8 , wherein the first ion store is an intermediate ion store, wherein the method further comprises:
 i) configuring the ion beam splitter to transfer precursor ions accumulated in the first ion store to a third ion store for analysis in a second mass analyser; or   ii) configuring the ion beam splitter to transfer precursor ions accumulated in the first ion store to the second ion destination.   
     
     
         10 . The method of  claim 9 , wherein the precursor ions transferred from the first ion store to i) the third ion store or ii) the second ion destination comprise the samples of precursor ions for each of the plurality of sub ranges. 
     
     
         11 . The method of  claim 9 , wherein the first ion store is provided by a DC barrier adjacent a first output region. 
     
     
         12 . The method of  claim 8 , wherein the ion beam splitter is configured to operate under pure molecular flow conditions. 
     
     
         13 . The method of  claim 8 , wherein the method further comprises fragmenting the precursor ions to produce the sample of fragmented precursor ions, wherein the second ion destination is the second ion store, wherein the ions are fragmented in the second ion store. 
     
     
         14 . The method of  claim 8 , wherein the method further comprises fragmenting the precursor ions to produce the sample of fragmented precursor ions, wherein the ions are fragmented using a multipole collision cell. 
     
     
         15 . The method of  claim 8 , further comprising, for each of the plurality of sub-ranges, configuring an ion filter to transmit precursor ions having m/z values within the sub-range, wherein the sample of precursor ions are received from the configured ion filter and sample of fragmented precursor ions are formed from fragmentation of precursor ions received from the configured ion filter. 
     
     
         16 . The method of  claim 15 , wherein configuring the ion filter comprises setting a transmission window of the ion filter, wherein the transmission window is adjusted between each of the plurality of sub-ranges, wherein for each sub-range, the transmission window for the step of accumulating the sample of precursor ions is the same as the transmission window for the step of injecting the sample of fragmented precursor ions into the first mass analyser or accumulating the sample of fragmented precursor ions. 
     
     
         17 . The method of  claim 16 , further comprising configuring an ion mobility separator to transfer precursor ions having m/z values within the sub-range to the ion filter. 
     
     
         18 . The method of  claim 17 , further comprising controlling the ion mobility separator so that the precursor ions transferred to the ion filter correspond with a transmission window of the ion filter, for each of the plurality of sub-ranges in the overall m/z range. 
     
     
         19 . The method of  claim 9 , wherein accumulating the sample of precursor ions comprises controlling a fill time for the precursor ions, based on a relative abundance of precursor ion species in the corresponding sub-range. 
     
     
         20 . The method of  claim 9 , wherein either:
 the second ion destination is a second ion store and the sample of fragmented precursor ions is accumulated in the second ion store, the method further comprising, for each of the plurality of sub-ranges, ejecting the sample of fragmented precursor ions from the second ion store into the first mass analyser and analysing the sample of fragmented precursor ions in the first mass analyser, wherein the plurality of sub-ranges comprises a first sub-range and a second sub-range, wherein the step of analysing the sample of fragmented precursor ions from the first sub-range at least partially overlaps with the step of accumulating, in the second ion store, the sample of fragmented precursor ions formed from fragmentation of precursor ions having m/z values within the second sub-range; or   the second ion destination is a first mass analyser and the sample of fragmented precursor ions are injected into the first mass analyser, the method further comprising analysing the sample of fragmented precursor ions in the first mass analyser, wherein the plurality of sub-ranges comprises a first sub-range and a second sub-range, wherein the step of analysing the sample of fragmented precursor ions from the first sub-range at least partially overlaps with the step of accumulating the sample of precursor ions having m/z values within the second sub-range in the first ion store.   
     
     
         21 . A mass spectrometer configured to perform the method of  claim 8 . 
     
     
         22 . One or more computer-readable media have stored thereon processor-executable instructions that, when executed by a processor of a computer, cause the computer to perform the method of  claim 8 .